Electronic device comprising semiconductor memory having ohmic-contact structure separated from current distributing layer

ABSTRACT

Disclosed are an LED and an LED module. The LED includes: a first conductivity type semiconductor layer; a mesa disposed over the first conductivity type semiconductor layer and including an active layer and a second conductivity type semiconductor layer; a first ohmic-contact structure in contact with the first conductivity type semiconductor layer; a second ohmic-contact structure in contact with the second conductivity type semiconductor layer; a lower insulating layer at least partially covering the mesa and the first conductivity type semiconductor layer and disposed to form a first opening part at least partially exposing the first ohmic-contact structure and a second opening part at least partially exposing the second ohmic-contact structure; and a current distributing layer connected to the first ohmic-contact structure at least partially exposed by the first opening part and disposed to form a third opening part at least partially exposing the second opening part.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent document claims priority from and the benefit of KoreanPatent Application No. 10-2013-0113296, filed on Sep. 24, 2013, which ishereby incorporated by reference in its entirety.

BACKGROUND

Exemplary embodiments of this patent document relates to a lightemitting diode (LED) and an LED module including a light emitting diodewhich can be adhered onto a printed circuit board, or the like by asolder paste, and an LED module having the same.

Since a gallium nitride (GaN) based light emitting diode (LED) has beendeveloped, the GaN based LED has been currently used for variousapplications such as a natural color LED display element, an LED trafficsignal, a white color LED, and the like.

The above information disclosed in this Background section is only forenhancement of understanding of the background of the invention and,therefore, it may contain information that does not constitute priorart.

SUMMARY

Exemplary embodiments of the patent document is to provide or caninclude providing a light emitting diode (LED) and an LED module capableof improving current distributing performance while also decreasinglight loss.

Exemplary embodiments of the patent document is to provide or caninclude providing a light emitting diode (LED) module having an LEDwhich is adhered onto a printed circuit board by solder paste.

Exemplary embodiments of the patent document is to provide or caninclude providing a light emitting diode (LED) and an LED module capableof preventing diffusion of metallic elements in a solder paste.

Additional features of the patent document will be set forth in thedescription which follows, and in part will become apparent from thedescription, or can be learned from practicing techniques, systems anddevices disclosed in the patent document.

An exemplary embodiment of the patent document discloses a lightemitting diode including: a first conductivity type semiconductor layer;a mesa disposed over the first conductivity type semiconductor layer andincluding an active layer and a second conductivity type semiconductorlayer; a first ohmic-contact structure in contact with the firstconductivity type semiconductor layer; a second ohmic-contact structurein contact with the second conductivity type semiconductor layer of themesa; a lower insulating layer covering the mesa and the firstconductivity type semiconductor layer, the lower insulating layerdisposed to form a first opening part at least partially exposing thefirst ohmic-contact structure and a second opening part at leastpartially exposing the second ohmic-contact structure; and a currentdistributing layer disposed over the lower insulating layer andelectrically connected to the first ohmic-contact structure at leastpartially exposed by the first opening part of the lower insulatinglayer, the current distributing layer disposed to form a third openingpart at least partially exposing the second opening part.

The light emitting diode can be implemented in various ways to includeone or more of the following features. The first ohmic-contact structureis formed to be separated from the current distributing layer, such thatthe range of choice of the metal material of the current distributinglayer is increased to improve light reflectivity of the currentdistributing layer.

The light emitting diode can include first ohmic-contact structures. Thecurrent distributing layer can electrically connect the firstohmic-contact structures to each other.

Since the first ohmic-contact structures are electrically connected toeach other using the current distributing layer, a current can be easilydistributed into the first ohmic-contact structures to improve currentdistributing performance of the light emitting diode. Since the currentdistributing layer can be formed across a wide area of the lightemitting diode, resistance of the current distributing layer can bereduced.

The current distributing layer can have a stacked structure differentfrom the first ohmic-contact structure and can include a metalreflective layer. The metal reflective layer can be a lowest layer inthe stacked structure of the current distributing layer. Light emittedthrough a side surface of the mesa is directly reflected from the metalreflective layer, and as a result, light loss due to the currentdistributing layer can be reduced.

Further, the light emitting diode can include a diffusion preventingreinforced layer disposed in a third opening part of the currentdistributing layer and connected to the second ohmic-contact structurewhich is at least partially exposed by the second opening part. Thediffusion preventing reinforced layer can have the same stackedstructure as the current distributing layer. It is possible to prevent ametal such as Sn from being diffused into the second ohmic-contactstructure by adopting the diffusion preventing reinforced layer.

The light emitting diode can include mesas and second ohmic-contactstructures connected to the second conductivity type semiconductorlayers on the respective mesas. The diffusion preventing reinforcedlayer can electrically connect the second ohmic-contact structures toeach other.

Further, the light emitting diode can include an upper insulating layercovering the current distributing layer. The upper insulating layer canbe disposed for form a fourth opening part defining a first electrodepad region by exposing the current distributing layer and a fifthopening part defining a second electrode pad region by at leastpartially exposing an upper region of the second ohmic-contactstructure.

The light emitting diode can include a diffusion preventing reinforcedlayer disposed in the third opening part of the current distributinglayer and connected to the second ohmic-contact structure which is atleast partially exposed by the second opening part, and the diffusionpreventing reinforced layer can be at least partially exposed to thefifth opening part.

The current distributing layer and the diffusion preventing reinforcedlayer can have the same structure and include a metal reflective layer.

The current distributing layer can include the metal reflective layer, adiffusion preventing layer, and an oxide preventing layer. Lightgenerated from the active layer can be reflected by the currentdistributing layer and the diffusion preventing reinforced layer anddiffusion of Sn, or the like can be prevented, such that the lightemitting diode can be mounted on the printed circuit board, or the likeusing the solder paste.

The current distributing layer can further include an adhesive layerdisposed over the oxide preventing layer. The adhesive layer improvesadhesion of the upper insulating layer which is disposed over thecurrent distributing layer and the current distributing layer.

According to another exemplary embodiment, there is provided a lightemitting diode module including a printed circuit board; and a lightemitting diode adhered onto the printed circuit board. The lightemitting diode can be any light emitting diode as described above, andcan be adhered onto the printed circuit board by a solder paste.

The light emitting diode module can be implemented in various ways toinclude one or more of the following features. The light emitting diodecan include: a first conductivity type semiconductor layer; a mesadisposed over the first conductivity type semiconductor layer andincluding an active layer and a second conductivity type semiconductorlayer; a first ohmic-contact structure being in contact with the firstconductivity type semiconductor layer; a second ohmic-contact structurebeing in contact with the second conductivity type semiconductor layerof the mesa; a lower insulating layer covering the mesa and the firstconductivity type semiconductor layer and disposed to form a firstopening part at least partially exposing the first ohmic-contactstructure and a second opening part at least partially exposing thesecond ohmic-contact structure; a current distributing layer connectedto the first ohmic-contact structure t least partially exposed by thefirst opening part of the lower insulating layer and having a thirdopening part at least partially exposing the second opening part; and anupper insulating layer covering the current distributing layer. Theupper insulating layer can be disposed to form a fourth opening partdefining a first electrode pad region by at least partially exposing thecurrent distributing layer and a fifth opening part defining a secondelectrode pad region by at least partially exposing an upper region ofthe second ohmic-contact structure which is at least partially exposedby the second opening part; and the first electrode pad region and thesecond electrode pad region can be respectively adhered to thecorresponding pads on the printed circuit board by the solder paste.

According to still another exemplary embodiment, there is provided amethod of manufacturing a light emitting diode, the method including:forming a first conductivity type semiconductor layer, an active layer,and a second conductivity type semiconductor layer over a substrate;forming a mesa over the first conductivity type semiconductor layer bypatterning the second conductivity type semiconductor layer and theactive layer; forming a first ohmic-contact structure contacting thefirst conductivity type semiconductor layer and a second ohmic-contactstructure contacting the second conductivity type semiconductor layer;forming a lower insulating layer which covers the mesa and the firstconductivity type semiconductor layer and disposed to form a firstopening part at least partially exposing the first ohmic-contactstructure and a second opening part at least partially exposing thesecond ohmic-contact structure; and forming a current distributing layerwhich is connected to the first ohmic-contact structure, on the lowerinsulating layer. The current distributing layer can be disposed to forma third opening part at least partially exposing the second openingpart.

Since the first ohmic-contact structure and the current distributinglayer are formed in separate processes, there is no need to form alowest layer of the current distributing layer using an ohmic metal,making it possible to reduce light loss due to the current distributinglayer.

The method can be implemented in various ways to include one or more ofthe following features. The method can include, during the forming ofthe current distributing layer, forming a diffusion preventingreinforced layer disposed in the third opening part. The diffusionpreventing reinforced layer can be formed of the same material and inthe same process as the current distributing layer, and as a result, thediffusion preventing reinforced layer can have the same stackedstructure as the current distributing layer.

The method can include forming an upper insulating layer covering thecurrent distributing layer and the upper insulating layer can bedisposed to form a fourth opening part at least partially exposing thecurrent distributing layer and a fifth opening part at least partiallyexposing the diffusion preventing reinforced layer.

The current distributing layer and the diffusion preventing reinforcedlayer which are at least partially exposed by the fourth opening partand the fifth opening part can be respectively used as electrode pads.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view for describing an exemplarylight emitting diode (LED) module according to an exemplary embodimentof the patent document.

FIGS. 2A, 2B, 3A, 3B, 4A, 4B, 5A, 5B, 6A, 6B, 6C, 7A, 7B, 7C, 8A, 8B,8C, 9A, 9B, 9C, and 9D are various views for describing an exemplarymethod of manufacturing a light emitting diode (LED) and an LED moduleaccording to an exemplary embodiment of the patent document. In therespective figures of FIGS. 2A through 8C, (A) shows a plan or top-downview, (B) shows a cross-sectional view taken along a dash line A-A, and(C) shows a cross-sectional view taken along a dash line B-B. FIG. 9A isa perspective view, FIG. 9B is a cross-sectional view taken along a dashline A-A, FIG. 9C is a cross-sectional view taken along a dash line B-B,and FIG. 9D is a cross-sectional view taken along a dash line C-C.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Hereinafter, exemplary embodiments of the patent document will bedescribed in detail with reference to the accompanying drawings. Theexemplary embodiments of the patent documents to be described below areprovided by way of example so that the idea of the patent document canbe sufficiently transferred to those skilled in the art to which thepatent document pertains. Therefore, the patent document is not limitedto exemplary embodiments described below, but can be implemented inother forms. In the accompanying drawings, widths, lengths, thicknesses,or the like, of components can be exaggerated for convenience. Likereference numerals denote like elements throughout the specification.

A GaN based LED is generally formed by depositing an epitaxial layer ona substrate made of sapphire, and includes an N-type semiconductorlayer, a P-type semiconductor layer, and an active layer interposedbetween the N- and P-type semiconductor layers. An N-electrode pad isformed on or disposed over the N-type semiconductor layer and aP-electrode pad is formed on or disposed over the P-type semiconductorlayer. The LED is electrically connected to an external power sourcethrough the electrode pads and is driven by the external power source.In this case, a current flows from the P-electrode pad to theN-electrode pad via the semiconductor layers.

In order to prevent light loss due to the p-electrode pad and increaseheat dissipating efficiency, an LED having a flip-chip structure canbeen used, and various electrode structures to assist in currentdistribution in the LED having a large scale flip-chip structure can beimplemented (see, for example, U.S. Pat. No. 6,486,499). For example,extensions for current distribution can be formed on or disposed overthe N-type semiconductor layer which is exposed by forming a reflectiveelectrode on the P-type semiconductor layer and etching the P-typesemiconductor layer and the active layer.

The reflective electrode formed on or disposed over the P-typesemiconductor layer can improve light emission efficiency by reflectinglight generated from the active layer and also assisting in the currentdistribution within the P-type semiconductor layer. The extensionsconnected to the N-type semiconductor layer can assist in the currentdistribution within the N-type semiconductor layer to allow light to beuniformly generated in a wide active region. In a large-scale LED havingan area of about 1 mm² or more which is used for a high output, currentdistribution within the N-type semiconductor layer together with thecurrent distribution with the P-type semiconductor layer tend to berequired.

However, there can be a limit in distributing the current due to the useof linear extensions increasing the resistance of the extensions.Further, since the reflective electrode is restrictively disposed on theP-type semiconductor layer, a significant amount of light is notreflected by the reflective electrode and is lost by the pads and theextensions.

In accordance with Korean Patent Laid Open Publication No.10-2013-0030178, for example, a current distributing layer that coversmesas and makes ohmic-contact with the N-type semiconductor layer can beadopted, such that the resistances of the extensions are decreased.Further, the current distributing layer can include a metal reflectivelayer to decrease light loss.

However, since the current distributing layer includes an ohmic-contactlayer and the metal reflective layer, light reflectivity of the currentdistributing layer can be low.

When the LED is used in a final product, it is or can be modularizedinto an LED module. The LED module generally includes a printed circuitboard (PCB) and an LED package mounted on the PCB, and the LED ismounted in a chip form in the LED package. An LED chip according to therelated art is mounted and packaged on a sub-mount, a lead frame, a leadelectrode, or the like using silver paste or AuSn solder, and the LEDpackage is then mounted on the PCB, or the like by solder paste.Accordingly, the pads on the LED chip are positioned to be far away fromthe solder paste and are adhered using an adhering material such assilver paste, AuSn, or the like which is relatively stable.

However, the pads of the LED can be directly adhered to the PCB, or thelike using the solder paste to manufacture the LED module. The LEDmodule can be manufactured by directly mounting the LED chip on the PCBwithout packaging the LED chip, or the LED module can be manufactured bymanufacturing the LED package of a so-called wafer level and mountingthe package on the PCB. In these cases, since the pads are directly incontact with the solder paste, metallic elements such as tin (Sn), andthe like in the solder paste are diffused into the LED through the pads,such that electrical short occurs in the LED and a device defect can becaused.

FIG. 1 is a schematic cross-sectional view for describing an exemplarylight emitting diode (LED) module according to an exemplary embodimentof the patent document.

Referring to FIG. 1, a light emitting diode (LED) module 10 includes aprinted circuit board 51 having pads 53 a and 53 b, and a light emittingdiode 100 which is adhered to the printed circuit board 51 by a solderpaste 55. In the example shown in FIG. 1, the solder paste 55 is used toconnect the LED 100 to the pads 53 a and 53 b of the printed circuitboard 51.

The printed circuit board 51, which is a board having a printed circuitformed on the board, is not particularly or in any way limited as longas the printed circuit board is structured for providing a lightemitting module.

For indirect mounting, a package is fabricated by mounting a lightemitting diode on a printed circuit board on which a lead frame or leadelectrodes are formed, and the package having the light emitting diodemounted is mounted on the printed circuit board. However, according tothe present exemplary embodiment, the light emitting diode 100 isdirectly mounted on the printed circuit board 51 by the solder paste 55without using a separate light emitting diode package.

The light emitting diode 100 is reversed or flipped over in a flip-chipform and is mounted on the printed circuit board 51. The light emittingdiode 100 has a first electrode pad region 43 a and a second electrodepad region 43 b so as to be mounted on the printed circuit board 51. Theabove-mentioned first and second electrode pad regions 43 a and 43 b canbe disposed to be recessed into one surface of the light emitting diode100 to form respective recessed areas for receiving the solder paste 55.

A lower surface, which faces up after flipping over the LED 100, of thelight emitting diode 100, that is, a surface opposite to the first andsecond electrode pad regions 43 a and 43 b can be covered with awavelength converter 45. The wavelength converter 45 can cover a sidesurface or surfaces substantially perpendicular to the lower surface inaddition to the lower surface of the light emitting diode 100.

Although FIG. 1 is schematically shown for convenience of explanation, astructure and the respective components of the light emitting diode 100will be more clearly understood by a method of manufacturing a lightemitting diode which is described below.

FIGS. 2A, 2B, 3A, 3B, 4A, 4B, 5A, 5B, 6A, 6B, 6C, 7A, 7B, 7C, 8A, 8B,8C, 9A, 9B, 9C and 9D are various views for describing an exemplarymethod of manufacturing a light emitting diode (LED) and an LED moduleaccording to an exemplary embodiment of the patent document. In therespective figures of FIGS. 2 A, 2B, 3A, 3B, 4A, 4B, 5A, 5B, 6A, 6B, 6C,7A, 7B, 7C, 8A, 8B, and 8C, (A) shows a plan view, (B) shows across-sectional view taken along a dash line A-A, and (C) shows across-sectional view taken along a dash line B-B. FIG. 9A is aperspective view, FIG. 9B is a cross-sectional view taken along a dashline A-A, FIG. 9C is a cross-sectional view taken along a dash line B-B,and FIG. 9D is a cross-sectional view taken along a dash line C-C.

First, referring to FIGS. 2A and 2B, a first conductivity typesemiconductor layer 23 is formed on or disposed over a substrate 21, andmesas M which are spaced apart from each other are formed on or disposedover the first conductivity type semiconductor layer 23. Each of themesas M respectively include an active layer 25 and a secondconductivity type semiconductor layer 27 disposed over the active layer25. Although FIGS. 2A and 2B of the present specification shows anddescribes a case in which three mesas M are formed to be spaced apartfrom each other, the total number of mesas M used can vary. For example,more than three mesas M can be formed and one or two mesas M can beformed.

The mesas M can be formed by depositing an epitaxial layer including thefirst conductivity type semiconductor layer 23, the active layer 25, andthe second conductivity type semiconductor layer 27 on the substrate 21using a metal organic chemical vapor deposition method, or the like andthen patterning the second conductivity type semiconductor layer 27 andthe active layer 25 so that the first conductivity type semiconductorlayer 23 is exposed at areas bordering the mesas M at all sides. Forexample, mesas M are formed by using etching to remove a portion of thefirst conductivity type semiconductor layer 23, the active layer 25, andthe second conductivity type semiconductor layer 27. The exposed areasof the first semiconductor layer 23 is substantially free of the secondconductivity type semiconductor layer 27 and the active layer 25. Sidesurfaces of the mesas M can be formed to be inclined from the activelayer 25 towards the second conductivity type semiconductor layer 27 byusing an appropriate technology such as photoresist reflow. An inclinedprofile of the side surface of the mesas M improves or can potentiallyimprove extraction efficiency of light generated from the active layer25.

The substrate 21, which is a board capable of receiving a deposition ofgallium nitride based semiconductor layer, can be, for example, asapphire-based printed circuit board, a silicon carbide-based printedcircuit board, a gallium nitride (GaN)-based printed circuit board, aspinel-based printed circuit board, or the like. For example, thesubstrate 21 can be a patterned printed circuit board such as apatterned sapphire-based printed circuit board.

For example, the first conductivity type semiconductor layer 23 caninclude an n-type gallium nitride based layer and the second conductivesemiconductor layer 27 includes or can include a p-type gallium nitridebased layer. In addition, the active layer 25 can have a single quantumwell structure or a multiple quantum well structure, and can include awell layer and a barrier layer. In addition, for the well layer, acomposition element can be selected depending on a required wavelengthof light and can include, for example, AlGaN, GaN, or InGaN. Dependingon a composition element of the active layer 25, the light emittingdiode 100 becomes or can become a light emitting diode emitting visiblelight or a light emitting diode emitting ultraviolet.

As shown in FIGS. 2A and 2B, in the case in which the mesas M are formedon or disposed over the first conducive type semiconductor layer 23, themesas M can be extended in parallel with each other in one sidedirection while having an elongated shape. As described above, mesas Mare formed by using etching to remove a portion of the firstconductivity type semiconductor layer 23, the active layer 25, and thesecond conductivity type semiconductor layer 27. This elongated shapesimplifies a process of forming the mesas M having the same shape invarious chip regions on the substrate 21.

Referring to FIGS. 3A and 3B, a first ohmic-contact structure 29 isformed on or disposed over the first conductivity type semiconductorlayer 23 at areas exposed by mesa etching. For example, the firstohmic-contact structure 29 can be formed or disposed between the mesas Mand edges along a length direction of the mesas M. As shown in FIG. 3,multiple ones of the first ohmic-contact structure 29 and the mesas Mare disposed over the first conductivity type semiconductor layer 23 inan alternative fashion. The first ohmic-contact structure 29 is formedof or includes a material which is in ohmic-contact with the firstconductivity type semiconductor layer 23, and can include, for example,titanium/aluminum (Ti/Al). In case of an ultraviolet light emittingdiode, the first ohmic-contact structure can have a stacked structure ofTi/Al/Ti/Au.

Although the present exemplary embodiment of FIGS. 3A and 3B shows anddescribes a case in which multiple ones of the first ohmic-contactstructures 29 are formed to be spaced apart from each other, a singleone of the first ohmic-contact structure 29 in which the multiple onesof the first ohmic-contact structures 29 are connected to each other canbe formed on or disposed over the first conductivity type semiconductorlayer 23.

Referring to FIGS. 4A and 4B, a second ohmic-contact structure 35 isformed on or disposed over each of the mesas M. The second ohmic-contactstructure 35 can be formed using a lift-off technology, for example. Thesecond ohmic-contact structure 35 is formed on or disposed over eachmesa M and has a shape which is substantially similar to that of themesa M. The second ohmic-contact structure 35 having the same structureas the corresponding mesa M can have a total surface area smaller thanor substantially similar to the total surface area of the correspondingmesa M.

The second ohmic-contact structure 35 can have different structuresdepending on or at least partially on a kind of light emitting diodeimplemented. For example, for a light emitting diode emittingultraviolet light of an ultraviolet-B (UVB) region and an ultraviolet-A(UVA) region which is close to the UVB region, the second ohmic-contactstructure 35 can include Ni/Au or Ni/Au and an adhesive layer.

In case of a blue light emitting diode or an ultraviolet light emittingdiode of the UVA region which is close to a blue light, the secondohmic-contact structure 35 can include a reflective metal part 31, acapping metal part 32, and an oxide preventing metal part 33. Thereflective metal part 31 can include at least one of an ohmic layer, areflective layer, or a stress alleviation layer disposed between thereflective metal part 31 and the capping metal part 32. The stressalleviation layer alleviates or substantially alleviates the stressgenerated due to a difference between coefficients of thermal expansionof the reflective metal part 31 and the capping metal part 32.

The reflective metal part 31 can be formed of or include, for example,Ni/Ag/Ni/Au, and can have a total thickness of about 1600 angstrom (Å).The reflective metal part 31 is formed or disposed so that a sidesurface is inclined as shown, that is, a bottom part has a relativelywider shape. The above-mentioned reflective metal part 31 can be formedby forming a photoresist pattern having opening parts exposing the mesasM and then using e-beam evaporation.

The capping metal part 32 covers or can cover an upper surface and aside surface or surfaces of the reflective metal part 31 to protect thereflective metal part 31. The capping metal part 32 can be formed byusing a sputtering technology or using e-beam evaporation (e.g.,planetary e-beam evaporation) tilting, rotating, and vacuum-depositingthe board 21. The capping metal part 32 can include Ni, Pt, Ti, or Cr,and can be formed by depositing, for example, about five pairs of Ni/Ptor about five pairs of Ni/Ti. In some implementations, the capping metalpart 32 can include TiW, W, or Mo.

The stress alleviation layer can be variously selected depending onmetal materials of the reflective layer and the capping metal part 32.For example, in the case in which the reflective layer is or includes Alor an Al alloy and the capping metal part or layer 32 includes W, TiW,or Mo, the stress alleviation layer can be or include a single layer ofAg, Cu, Ni, Pt, Ti, Rh, Pd, or Cr, or can be or include a compositelayer of Cu, Ni, Pt, Ti, Rh, Pd, or Au. In addition, in the case inwhich the reflective layer is or includes Al or an Al alloy and thecapping metal part 32 is or includes Cr, Pt, Rh, Pd, or Ni, the stressalleviation layer can be or includes a single layer of Ag, or Cu, or canbe or include a composite layer of Ni, Au, Cu, or Ag.

In addition, in the case in which the reflective layer is Ag or an Agalloy and the capping metal part 32 includes W, TiW, or Mo, the stressalleviation layer can be or includes a single layer of Cu, Ni, Pt, Ti,Rh, Pd, or Cr, or can be or include a composite layer of Cu, Ni, Pt, Ti,Rh, Pd, Cr, or Au. In addition, in the case in which the reflectivelayer is Ag or an Ag alloy and the capping metal part 32 is Cr or Ni,the stress alleviation layer can be or include a single layer of Cu, Cr,Rh, Pd, TiW, or Ti, or can be or include a composite layer of Ni, Au, orCu.

In addition, an oxidation preventing metal part 33 includes Au in orderto prevent oxidation of the capping metal part 32, and can be formed ofor include, for example, Au/Ni or Au/Ti. Ti is an effective choice sinceTi has good adhesion with an oxidation layer such as SiO₂. The oxidationpreventing metal part 33 can be formed by using a sputtering or usinge-beam evaporation (e.g., planetary e-beam evaporation) tilting,rotating, and vacuum-depositing the substrate 21.

The second ohmic-contact structure 35 is deposited and the photoresistpattern is then removed, such that the second ohmic-contact structure 35is left on the second conductivity type semiconductor layer 27 as shownin FIGS. 4A and 4B.

Although the present exemplary embodiment as shown in FIGS. 4A and 4Bdescribes a case in which the mesas M, the multiple ones of the firstohmic-contact structure 29, and the second ohmic-contact structure 35are formed in sequence, an order of forming these components can bevaried. For example, the second ohmic-contact structure 35 can be formedbefore the first ohmic-contact structure 29 is formed, and can also beformed before the mesa M is formed.

Referring to FIGS. 5A and 5B, after the first and second ohmic-contactstructures are formed, a lower insulating layer 37 is formed to coverthe mesas M and the first conductivity type semiconductor layer 23. Thelower insulating layer 37 can be formed by an oxide film such as SiO₂,or the like, a nitride film such as SiNx, or the like, and an insulatingfilm such as MgF₂, or the like using a technology such as chemical vapordeposition, or the like. The lower insulating layer 37 can be formed tohave a thickness of, for example, 4000 to 12000 Å. The lower insulatinglayer 37 can be formed by a single layer, but is not limited to a singlelayer. For example, the lower insulating layer 37 can be formed by amulti-layer. Further, the lower insulating layer 37 can be formed by adistributed Bragg reflector (DBR) in which a low refractive indexmaterial layer and a high refractive index material layer arealternately stacked. For example, an insulating reflective layer havinghigh reflectivity can be formed by stacking a layer such as SiO₂/TiO2,SiO₂/Nb₂O₅, or the like.

A dividing region 23 h dividing the lower insulating layer 37 and thefirst conductivity type semiconductor layer 23 into a chip unit can beformed using a laser scribing technology. A groove can also be formed inan upper surface (e.g. the surface in contact with the firstconductivity type semiconductor layer 23) of the substrate 21 by thelaser scribing. As a result, the substrate 21 is exposed in the vicinityof edges of the first conductivity type semiconductor layer 23.

Since the first conductivity type semiconductor layer 23 is divided intothe chip unit using the laser scribing technology, a separate photomaskis not used.

Although the present exemplary embodiment shows a case in which thelower insulating layer 37 and the first conductivity type semiconductorlayer 23 are divided into the chip unit using the laser scribingtechnology after the lower insulating layer 37 is formed, the firstconductivity type semiconductor layer 23 can be divided into the chipunit using the laser scribing technology before the lower insulatinglayer 37 is formed.

Referring to FIGS. 6A, 6B and 6C, by patterning the lower insulatinglayer 37, first opening parts 37 a exposing or partially exposing thefirst ohmic-contact structures 29 are formed, and second opening parts37 b exposing or partially exposing the second ohmic-contact structures35 are formed.

As shown in FIG. 6A, the second opening parts 37 b can be formed on ordisposed over the respective mesas M in a state which is leaned to anedge of one side of the substrate 21 to expose a portion of therespective mesas M. In addition, the first ohmic-contact structures 29disposed between the second opening parts 37 b are covered or partiallycovered with the lower insulating layer 37 as shown in FIGS. 6B and 6C.

The subset of the first ohmic-contact structures 29 which are disposedat the edges of the board 21 among the first ohmic-contact structures 29can be fully exposed by the first opening parts 37 a. However, in caseof the first ohmic-contact structures 29 which are disposed between themesas M, in order to prevent the first ohmic-contact structure 29 andthe second ohmic-contact structure 35 from being short-circuited in asubsequent process, the regions of the first ohmic-contact structure 29exposed by the first opening parts 37 a are disposed to be spaced apartfrom regions between the second opening parts 37 b. The locations of thefirst opening parts 37 a and second opening parts 37 b are arranged toavoid overlapping along the same lateral line.

Referring to FIGS. 7A, 7B and 7C, a current distributing layer 39 isformed on or disposed over the lower insulating layer 37. The currentdistributing layer 39 covers or substantially covers the mesas M and thefirst conductivity type semiconductor layer 23. In addition, the currentdistributing layer 39 has a third opening part 39 a exposing orpartially exposing the second opening parts 37 b. The third opening part39 a exposes or partially exposes the second ohmic-contact structures 35which are exposed or partially exposed by the second opening parts 37 b.Therefore, the current distributing layer 39 is insulated from the mesasM and the second ohmic-contact structures 35 by the lower insulatinglayer 37.

The current distributing layer 39 is electrically connected to the firstohmic-contact structures 29 through the first opening parts 37 a of thelower insulating layer 37. The first ohmic-contact structures 29 whichare spaced apart from each other can be electrically connected to eachother through the current distributing layer 39. Further, the currentdistributing layer 39 can cover side surfaces of the first ohmic-contactstructures 29, and as a result, light incident onto the side surfaces ofthe first ohmic-contact structures 29 can be reflected from the currentdistributing layer 39.

As shown in FIGS. 7A, 7B and 7C, since the current distributing layer 39covers most of the regions on the substrate 21, the current distributionlayer 39 has a low resistance, making it possible to easily distribute acurrent into the first ohmic-contact structures 29.

The current distributing layer 39 can include a metal reflective layer,a diffusion preventing layer, and an oxide preventing layer. Further,the metal reflective layer can be a lowest layer of the currentdistributing layer 39. The metal reflective layer of the currentdistributing layer 39 reflects light which is incident onto the currentdistributing layer 39 to increase reflectivity of the light emittingdiode. Al can be used as the metal reflective layer. In addition, thediffusion preventing layer prevents diffusion of metal atom to protectthe metal reflective layer in the current distributing layer 39. Forexample, the diffusion preventing layer in the current distributinglayer 39 can prevent the diffusion of metal atom such as Sn in thesolder paste. The diffusion preventing layer can include Cr, Ti, Ni, Mo,TiW or W, or a combination of Cr, Ti, Ni, Mo, TiW or W. Mo, TiW, and Wcan be formed in a single layer. Cr, Ti, and Ni can be formed in a pair.For example, the diffusion preventing layer can include at least twopairs of Ti/Ni or Ti/Cr. The oxide preventing layer can be formed toprevent an oxidation of the diffusion preventing layer and can includeAu.

The current distributing layer 39 has an improved reflectivity thanother competing current distributing layer that includes theohmic-contact layer in the lowest layer. Therefore, light loss generateddue to light absorption of the current distributing layer 39 can bedecreased.

Further, the current distributing layer can include an adhesive layerdisposed on the oxide preventing layer. The adhesive layer can includeTi, Cr, Ni, or Ta. The adhesive layer can be used to improve adhesion ofthe current distributing layer and the upper insulating layer, and canalso be omitted.

For example, the current distributing layer 39 can have a multi-layerstructure of Al/Ni/Ti/Ni/Ti/Au/Ti.

While the current distributing layer 39 is formed, a diffusionpreventing reinforced layer 40 can be formed in the third opening part39 a. The diffusion preventing reinforced layer 40 can be formed of orinclude the same material and formed by the same process as that of thecurrent distributing layer 39. The diffusion preventing reinforced layer40 can have the same stacked structure as that of the currentdistributing layer 39.

The diffusion preventing reinforced layer 40 is spaced apart from thecurrent distributing layer 39 and is connected to the secondohmic-contact structures 35 which are exposed or partially exposed bythe second opening parts 37 b. The second ohmic-contact structures 35which are spaced apart from each other by the diffusion preventingreinforced layer 40 can be electrically connected to each other. Inaddition, as shown in FIG. 7C, the diffusion preventing reinforced layer40 is insulated from the first ohmic-contact structures 29 by the lowerinsulating layer 37.

In order to prevent light loss, the current distributing layer 39 andthe diffusion preventing reinforced layer 40 can cover 80% or more of atotal chip area.

Referring to FIGS. 8A, 8B and 8C, an upper insulating layer 41 is formedon or disposed over the current distributing layer 39. The upperinsulating layer 41 has an opening part 41 a defining a first pad region43 a by exposing or partially exposing the current distributing layer 39and an opening part 41 b defining a second pad region 43 b by exposingor partially exposing the diffusion preventing reinforced layer 40. Theopening parts 41 a and 41 b can have an elongated shape in a directionperpendicular to the mesas M. Meanwhile, the opening part 41 b of theupper insulating layer 41 has an area narrower or smaller than theopening part 39 a of the current distributing layer 39 and can furtherhave an area narrower or smaller than that of the diffusion preventingreinforced layer 40. Therefore, the upper insulating layer 41 covers aside wall or walls of the third opening part 39 a.

In the case in which the diffusion preventing reinforced layer 40 isomitted, the opening part 41 b exposes or partially exposes the secondopening parts 37 b and further exposes or partially exposes the secondohmic-contact structures 35 which are exposed or partially exposed bythe second opening parts 37 b. In this case, the second ohmic-contactstructures 35 can be used as the second pad region.

In addition, the upper insulating layer 41 can also be formed on ordisposed over the chip dividing region 23 h, covering the side surfaceor surfaces of the first conductivity type semiconductor layer 23.Therefore, it is possible to prevent substantially prevent permeation ofmoisture, or the like through upper and lower interfaces of the firstconductivity type semiconductor layer.

The upper insulating layer 41 can be formed by a silicon nitride film toprevent metal elements of the solder paste from being diffused, and canbe formed to have a thickness of 1 or more to 2 μmr less. In the case inwhich the thickness of the upper insulating layer 41 is less than 1 μmit is difficult to prevent the diffusion of the metal elements of thesolder paste.

Selectively, Sn diffusion preventing plated layers (not shown) can beadditionally formed on or disposed over the first electrode pad region43 a and the second electrode pad region 43 b using an electrolessplating technology such as electroless nickel immersion gold (ENIG).

The first electrode pad region 43 a is electrically connected to thefirst conductivity type semiconductor layer 23 through the currentdistributing layer 39 and the first ohmic-contact structure 29, and thesecond electrode pad region 43 b is electrically connected to the secondconductivity type semiconductor layer 27 through the diffusionpreventing reinforced layer 40 and the second ohmic-contact structure35.

The first electrode pad region 43 a and the second electrode pad region43 b can be used to mount the light emitting diode on the printedcircuit board, or the like by the solder paste. Therefore, in order toprevent an electrical short circuit between the first electrode padregion 43 a and the second electrode pad region 43 b due to the solderpaste, a distance between the electrode pads can be about 300 μm ormore.

Thereafter, the lower surface of the substrate 21 is partially removedby a grinding and/or lapping process, making it possible to reduce athickness of the substrate 21. The light emitting diodes which areseparated from each other, are manufactured by dividing the substrate 21into a separate chip unit. In this case, the substrate 21 can be dividedfrom the dividing region 23 h formed by using the laser scribingtechnology, and therefore, the laser scribing need not to beadditionally performed in order to perform the chip division.

The substrate 21 can be removed from the chip unit of the light emittingdiode before or after being divided into a separate light emitting diodechip unit.

Referring back to FIG. 1, the wavelength converter 45 of FIG. 1 can beformed on or disposed over the light emitting diodes 100 which areseparated from each other after dicing of wafer. The wavelengthconverter 45 can be formed using various fabrication processes includingby coating a resin containing a fluorescent substance on the lightemitting diode using a printing method, or coating fluorescent powder onthe substrate 21 using an aerosol spraying apparatus. Since afluorescent thin film having a uniform thickness can be formed on ordisposed over the light emitting diode by using an aerosol depositionmethod, color uniformity of light emitted from the light emitting diodecan be improved. Disposing the wave converter 45 over light emittingdiode as described above finishes or completes fabrication of the lightemitting diode according to an exemplary embodiment of the presentpatent document, and the completed light emitting diode is adhered tocorresponding pads 53 a and 53 b of a printed circuit board 51 by asolder paste as shown in FIG. 1, such that a light emitting diode moduleis finished or completed.

Referring to FIGS. 9A, 9B, 9C and 9D, FIG. 9A shows a schematicperspective view of the light emitting diode module, FIG. 9B shows across-sectional view of the light emitting diode module taken along adash line A-A of FIG. 9A, FIG. 9C shows a cross-sectional view of thelight emitting diode module taken along a dash line B-B of FIG. 9A, andFIG. 9D shows a cross-sectional view of the light emitting diode moduletaken along a dash line C-C of FIG. 9A. Unlike the exemplary embodimentof FIG. 1, the wavelength converter is omitted for illustrative purposesonly or merely to enhance the explanation of the present exemplaryembodiment of the patent document, but is not limited by the absence ofpresence of the wavelength converter.

As shown in FIGS. 9A, 9B, 9C and 9D, at least a portion of the solderpaste 55 is disposed in the first electrode pad region 43 a and thesecond electrode pad region 43 b and is adhered to the correspondingpads 53 a and 53 b, respectively, of the printed circuit board 51, suchthat fabrication of the light emitting diode module according to thepresent patent document can be finished or completed.

According to exemplary embodiments of the present patent document, thefirst ohmic-contact structure 29 is formed separately from the currentdistributing layer 39, such that the range of choice of the metalmaterial of the current distributing layer 39 is increased, making itpossible to improve light reflectivity of the current distributing layer39. Further, the light emitting diode (LED) and the LED module havingthe same capability of preventing diffusion of the metal elements in thesolder paste 55 using the current distributing layer 39 and thediffusion preventing reinforced layer can be provided. Further, thelight emitting diode having improved current distributing performance,particularly, a flip-chip type light emitting diode can be provided.

Only a few embodiments, implementations and examples are described andother embodiments and implementations, and various enhancements andvariations can be made based on what is described and illustrated inthis document.

What is claimed is:
 1. A light emitting diode comprising: a firstconductivity type semiconductor layer; a plurality of mesas disposedover the first conductivity type semiconductor layer and including anactive layer and a second conductivity type semiconductor layer; a firstohmic-contact structure in contact with the first conductivity typesemiconductor layer; a plurality of second ohmic-contact structures incontact with the second conductivity type semiconductor layer of themesa; a lower insulating layer covering the mesa and the firstconductivity type semiconductor layer, the lower insulating layer havinga first opening part exposing the first ohmic-contact structure and asecond opening part exposing the second ohmic-contact structure; acurrent distributing layer electrically connected to the firstohmic-contact structure exposed by the first opening part of the lowerinsulating layer, the current distributing layer having a third openingpart exposing the second opening part; and a diffusion preventingreinforced layer disposed in the third opening part of the currentdistributing layer and connected to the second ohmic-contact structureexposed by the second opening part, wherein the diffusion preventingreinforced layer electrically connects the plurality of secondohmic-contact structures to each other, wherein the light emitting diodefurther comprises an upper insulating layer covering the currentdistributing layer, wherein the upper insulating layer is disposed toform a fourth opening part defining a first electrode pad region byexposing the current distributing layer and a fifth opening partdefining a second electrode pad region by exposing an upper region ofthe diffusion preventing reinforced layer, and wherein the currentdistributing layer and the diffusion preventing reinforced layer havethe same structure and include a metal reflective layer.
 2. The lightemitting diode of claim 1, wherein the light emitting diode includes aplurality of first ohmic-contact structures, and the currentdistributing layer electrically connects the plurality of firstohmic-contact structures to each other.
 3. The light emitting diode ofclaim 1, wherein the current distributing layer has a stacked structuredifferent from the first ohmic-contact structure and includes a metalreflective layer.
 4. The light emitting diode of claim 3, wherein themetal reflective layer is a lowest layer in the stacked structure of thecurrent distributing layer.
 5. The light emitting diode of claim 1,wherein the diffusion preventing reinforced layer and the currentdistributing layer have a same stacked structure.
 6. The light emittingdiode of claim 1, wherein the current distributing layer includes themetal reflective layer, a diffusion preventing layer, and an oxidepreventing layer.
 7. The light emitting diode of claim 6, wherein thecurrent distributing layer includes an adhesive layer disposed on theoxide preventing layer.
 8. The light emitting diode of claim 1, whereinthe plurality of mesas have inclined side surfaces.
 9. The lightemitting diode of claim 1, wherein the first conductivity typesemiconductor layer includes an n-type gallium nitride layer and thesecond conductivity type semiconductor layer includes a p-type galliumnitride layer.
 10. The light emitting diode of claim 1, wherein thefirst ohmic-contact structures include titanium or aluminum or the both.11. The light emitting diode of claim 1, wherein the secondohmic-contact structures include a reflective metal part, a cappingmetal part, and an oxide preventing metal part.
 12. The light emittingdiode of claim 1, wherein the lower insulating layer has a thicknessbetween 4000 Å to 12000 Å.
 13. The light emitting diode of claim 1,wherein the lower insulating layer includes a distributed Braggreflector (DBR).
 14. A light emitting diode module comprising: a printedcircuit board; and a light emitting diode adhered onto the printedcircuit board, wherein the light emitting diode includes: a firstconductivity type semiconductor layer; a plurality of mesas disposedover the first conductivity type semiconductor layer and including anactive layer and a second conductivity type semiconductor layer; a firstohmic-contact structure in contact with the first conductivity typesemiconductor layer; a plurality of second ohmic-contact structures incontact with the second conductivity type semiconductor layer of themesa; a lower insulating layer covering the mesa and the firstconductivity type semiconductor layer and disposed to form a firstopening part at least partially exposing the first ohmic-contactstructure and a second opening part exposing the second ohmic-contactstructure; a current distributing layer electrically connected to thefirst ohmic-contact structure exposed by the first opening part of thelower insulating layer, the current distributing layer disposed to forma third opening part exposing the second opening part; a diffusionpreventing reinforced layer disposed in the third opening part of thecurrent distributing layer and connected to the second ohmic-contactstructure exposed by the second opening part; and an upper insulatinglayer covering the current distributing layer, wherein the upperinsulating layer is disposed to form a fourth opening part defining afirst electrode pad region by at least partially exposing the currentdistributing layer and a fifth opening part defining a second electrodepad region by exposing an upper region of the diffusion preventingreinforced layer; the diffusion preventing reinforced layer electricallyconnects the plurality of second ohmic-contact structures to each other;the first electrode pad region and the second electrode pad region arerespectively adhered to the corresponding pads on the printed circuitboard by a solder paste; and the current distributing layer and thediffusion preventing reinforced layer have the same structure andinclude a metal reflective layer.
 15. The light emitting diode module ofclaim 14, wherein the current distributing layer includes a metalreflective layer, the metal reflective layer being a lowest layer in astacked layer structure of the current distributing layer.